Clark, 50, was the heavy favorite in Tuesday’s election, benefiting from running in a Democratic-leaning district where President Barack Obama won 65 percent of the vote last year. She also had a significant financial advantage over her obscure Republican opponent, outraising him by $1.4 million to $86,000.

Clark had the backing of the women’s group EMILY’s List, which spent around $200,000 in the race. In October, she prevailed over a crowded field of Democratic primary opponents.

With Clark’s win, the nine-seat Massachusetts congressional delegation remains entirely in Democratic control. The last time Massachusetts Republicans won a U.S. House race was 1994.